[u:]
A long /u/ as in: moon /muːn/, fool
/fuːl/, cool /kuːl/; tongue body
is pulled back, it’s a back vowel and a
high/ close vowel as also it´s a tense vowel.

[ɔː] A long vowel sound as in: all /ɔːl/, or /ɔːr/, call /kɔːl/, born /bɔːn/, store /stɔːr/; The tongue body is pulled back, it’s a back vowel and the tongue body is intermediate as also it’s a tense vowel.

Here you are similar pairs of short vowels:

/ə/- at /ət/, an /ən/, about /əˈbaʊt/, under /ˈʌn.dər/, mother /ˈmʌð.ər/ ; It’s a lax vowel, the tongue body is neutral and it’s a mid vowel.

[ɒ] - on /ɒn/, off /ɒf/, dog /dɒg/, pot /pɒt/; It’s a lax vowel.

[ʊ] – book /bʊk/, cook /kʊk/, look /lʊk/; it’s a lax vowel as also a high back rounded vowel.

The
similar pairs of long and short vowels:

[ə] –
at /ət/,
an /ən/,
about /əˈbaʊt/, under /ˈʌn.dər/
, mother /ˈmʌð.ər/

[ɜ:]
– girl /gɜːl/, hurt /hɜːt/

[ɒ]
- on /ɒn/, off /ɒf/,
dog /dɒg/, pot /pɒt/

[ɔː]–
a long vowel sound as in: all /ɔːl/,
or /ɔːr/, call /kɔːl/, born /bɔːn/,
store /stɔːr/

[ʊ] –
book /bʊk/,
cook /kʊk/, look /lʊk/

[u:]
moon /muːn/, fool /fuːl/,
cool /kuːl/

The difference in pronunciation betweena
long and a short vowel lies in the position of the tongue. When pronouncing
long sounds, we place the middle of the tongue against the top of the mouth. On
the other hand, when we pronounce short sounds the middle of the tongue stays
in a lower position.

Since I´m a lover of technology I would use interactive exercises in the
classroom. I think it helps the motivation of our pupils in the classroom when
we have to do repetitive pronunciation activities. I think the activities I´ve
listed below are good for learning and also having fun at the same time:

Length is a feature which is very present in English
vowels, yet a feature unknown for Spaniards.
There is a series of factors such as the point, and tension of
articulation, which determine the length of a vowel sound.

For this task you are required to state which the five pure long English vowels are (not
diphthongs or triphthongs), and also elicit the similar pairs of short vowels.

You will therefore, create a list of similar pairs of long and short vowels (for example
/i/ and /i:/), and describe
them in detail, providing examples. You will have to explain differences in quality, tongue position,
and lip position.

Finally, you shall design a couple of exercises, to be carried out in class with
young children, that would help solving these difficulties when it comes to
distinguishing short and long vowels.